The present invention relates to a restriction enzyme inhibitor comprising the hot water extract of seaweeds, etc. The restriction enzyme inhibitor of the present invention is capable of selectively inhibiting a target restriction enzyme without decomposing any exogenous DNA and it has the added advantage of ease of preparation.
Restriction enzymes are endonucleases having a site specificity for DNA which are capable of cutting and eliminating an exogenous DNA which invades cells either in the form of a virus or as naked DNA. Commonly employed restriction enzymes include HindIII, EcoRI, BamHI, BgII, PstI, etc. It is often required in practical operations of genetic engineering to prevent the decomposition of exogenous DNAs by inhibiting the action of restriction enzymes but heretofore, no restriction enzyme inhibitor has been available that can be produced by a simple method at low cost.